A new phenotype of myorhythmia: Oculofacial myorhythmia in a patient with Erdheim Chester disease.

Oculofacial myorhythmia (OFM) is a movement disorder characterized by slow, rhythmic, and repetitive movement that affects the periorbital and perioral muscles. This abnormal movement is classified as a tremor and is highly suggestive of brainstem lesions. Unlike the oculomasticastory myorhythmia, the oculofacial pattern has rarely been reported to date. We present a patient diagnosed with Erdheim Chester disease who two years after the diagnosis developed an oculofacial myorhythmia. We additionally provide a pathological framework based on evolutionary changes on neuroimaging which could explain the appearance of this very rare movement disorder. No cases of OFM have been described in patients with ECD to date. To our knowledge we are reporting the first case of oculofacial myorhythmia secondary to Erdheim Chester disease. To conclude, oculofacial myorhytmia could be a late-onset clinical manifestation of ECD with brainstem involvement.